1. Field of the Invention
The present invention relates to a cleaning device for cleaning an intermediate transfer member and to an image forming apparatus equipped with the cleaning device.
2. Description of the Background Art
Conventionally, a color image forming apparatus has been known which adopts a one-path two-side transfer system. In such a color image forming apparatus, which adopts the one-path two-side transfer system, a part of a first intermediate transfer belt and a part of a second intermediate transfer belt are opposed to each other with a transfer sheet therebetween. Due to this arrangement, a toner image formed on the first intermediate transfer belt by means of a photosensitive member is transferred to the front surface of the transfer sheet. At the same time, a toner image transferred in advance to the second intermediate transfer belt by way of the first intermediate transfer belt is transferred to the back surface of the recording medium. In this way, by transporting the transfer sheet only one time, it is possible to transfer synthetic toner images to both sides of the transfer sheet. Any residual toner not transferred to the transfer sheet but remaining on the intermediate transfer belts is removed by cleaning means respectively provided for the intermediate transfer belts.
When an image is to be transferred to one side of a transfer sheet, a toner image is formed solely on the first intermediate transfer belt, and this toner image is transferred to one side of the transfer sheet. By means of a cleaning blade serving as a cleaning means for cleaning the first intermediate transfer belt, any residual toner on the first intermediate transfer belt is removed, and a cleaning blade for cleaning the second intermediate transfer belt removes any paper powder adhering to the second intermediate transfer belt. Residual toner on an intermediate transfer belt is electrostatically attracted onto the intermediate transfer belt, so that it cannot be completely removed just by bringing a cleaning blade into contact with the intermediate transfer belt.
Thus, a powerful cleaning means is needed. For example, it is necessary to apply a voltage to the cleaning blade, etc. to generate an electric field, and to reduce, by the action of this electric field, the electrostatic attracting force acting on the residual toner on the intermediate transfer belt, performing cleaning with the cleaning blade in this state.
In contrast, when the transfer of an image is to be performed solely to one side of a transfer sheet, the cleaning to be performed on the second intermediate belt solely involves the removal of paper powder; by bringing the cleaning blade into contact with the second intermediate transfer belt, the removal of paper powder is possible without involving any load on the second intermediate transfer belt.
In the prior-art technique, however, even when image transfer is to be effected only on one side of the transfer sheet, a powerful cleaning means suitable for the removal of residual toner is used as the cleaning means for the second intermediate transfer belt. The use of a cleaning means more powerful than necessary results in an unnecessary load on the second intermediate transfer belt, which may lead, in some cases, to a reduction in the service life of the intermediate transfer belt. On the other hand, if, to reduce the load on the intermediate transfer belt, a cleaning means with weak cleaning power is used, the residual toner cannot be completely removed, so that there is a fear of the cleaning being rather insufficient.